Protein Synthesis

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Protein Synthesis: Overview


DNA's Role
  • DNA stores/transmits information
  • This information directs cell activities
  • Proteins are the products of the DNA message

Proteins
  • Proteins are found in meat, the human body, dairy products, beans, etc.
  • Enzymes are proteins that cause chemical reactions
  • They are large 3-D molecules made of folded and twisted sub-units called "Amino Acids"

Amino Acids
  • Have 3 parts:
    • An Amine Group
    • An Acid Group
    • An "R" Group (20 types)
external image amino_acid_structure_2.jpg
  • Amino Acid forms a chain of acids called a polypeptide.
    • Arrangement of Amino Acids is based on information from the DNA
  • Then it folds and twists itself into a protein.
    • Shape of protein based on the chemistry of the "R" group
      • Some attract/repel each other depending on if they're polar or nonpolar
      • Some, like sulfides bond covalently forming a "bridge"

Protein Production
  • DNA base sequence is important
  • Sequence is transcribed in nucleus onto an RNA strand
  • RNA is translated into an Amino Acid sequence (polypeptide chain)
  • Polypeptides are edited, folded, and jointed together to make a protein.

Genetic Code
external image genetic%20code.jpg
  • 3 "letters" make 1 amino acid "word"
  • The code is redundant
  • Multiple combinations form one amino acid in order to prevent mistakes

Funny human demo of protein synthesis.


Transcription

Transcription is the process of making Messenger RNA from a DNA template to carry the code for a specific gene to the ribosome where it is translated into a polypeptide chain.

Promoter (TATA) ----transcription unit (gene)-----Terminator
  • Helicase unzips DNA.
  • RNA polymerase creates a RNA strand that is complementary to the DNA strand (but instead of Thymine there is Uracil).
  • This single strand is called messenger RNA and it travels to the ribosome where it gets translated.



Translation

  1. Messenger RNA (M-RNA) formed in transcription carries the coded information from the DNA to the ribosome.
  2. T-RNA moves to the attachment sight on the ribosome and attaches its anti-codons to the respective codons (group of 3 m-RNA nucleotides) on the M-RNA.
  3. These anti-codons code for specific Amino Acids which (as the T-RNA attaches more anti-codons ) bond to form a polypeptide chain.
  4. The Polypeptide chain may combine with other polypeptide chains to form specific proteins.